Space propulsion techniques can be divided into a chemical propulsion and an electric propulsion, as well as some other propulsion techniques (such as solar sail, tethered propulsion and the like). At present, most main thrusters of spacecraft employ chemical propulsion. But as an advanced propulsion technique, electric propulsion is getting more and more attention.
Chemical propulsion is a kind of propulsion technique using chemical energy to send the spacecraft into the reserved space orbit and realizes orbit maneuver. The most prominent feature of chemical propulsion is high propulsion, which is the most used technique in the space field. A chemical engine is used in the present long-life tri-axial attitude control stabilized satellite and spin satellite as a controlling and executing assembly. There are two work modes of the chemical engine: pulsating work and stability work. The pulsating work is mostly used in satellite attitude-adjusting and position-retaining; while the stability work is mostly used in satellite-orbit maneuver.
An electric propulsion system provides energy to a propellant using electricity generated by a solar panel or a nuclear reactor, to make the propellant produce a jet velocity far more than a common chemical thruster. High specific impulse of electric propulsion can reduce the system quality, save the propellant, improve the lifetime and increase payload. Besides applying in a long-life communication satellite to improve the performance of the satellite platform, the electric propulsion can complete the tasks which a common propulsion system is unable to do.
Both chemical propulsion and electric propulsion need to carry certain propellants, which not only occupy the weight of a spacecraft platform but also greatly increase the launch costs. Meanwhile in-orbit maneuver life of a spacecraft mainly depends on the quantity of carried fuel. A propulsion mode depends on the carried fuels and seriously restricts the spacecraft platform function extension and service life prolongation. So, the present international space field is actively developing all kinds of propulsion techniques based on the use of space environment. All the new techniques, including solar sail, magnetic sail, magnetic engine or the like, are developed based on the use of space environment using light, electric, magnetic and the like.